-LRB- CNN -RRB- -- Rescuers are looking for two missing hikers after finding a third dead on the slopes of Oregon 's Mount Hood , but the search has been hindered by the threat of avalanches , a sheriff 's deputy said Sunday .

The hikers began their climb at about 1 a.m. PT Friday . Authorities received a call that they were missing at about 10 p.m. Friday , said Deputy Scott Meyers of the Clackamas County Sheriff 's Office .

They planned a fairly easy , `` semi-technical '' hike in which they would come down the south side of the mountain , Meyers said .

Authorities followed what they believed to be the planned path , and on Saturday found the body of one of the hikers , identified as Luke T. Gullberg , 26 , of Des Moines , Washington .

Search and rescue personnel were unable to locate the others -- Anthony Vietti , 24 , of Longview , Washington , and Katie Nolan , 29 , of Portland , Oregon .

Coverage from CNN affiliate KPTV

`` This is still called a rescue operation , at least for a couple days , '' Meyers said Sunday , meaning authorities hold out hope of finding the hikers alive in the freezing conditions . `` We have reason to believe one of the two missing hikers has a bivvy sack , kind of like a lightweight sleeping bag . The female hiker is fairly well prepared for this climb -- she did have some stuff to warm up with . ''

`` We 're looking at the area where we found the body , '' he said . `` We think they may have dug into that area and just ca n't get down . ''

But the threat of avalanches `` is too high to go forward with a full ground rescue operation , '' Meyers said .

Another deputy , Jim Strovink , said there is `` a high level of danger for avalanche potential on Mount Hood . ''

A U.S. Coast Guard C-130 aircraft was coming to help in the search , and an Oregon National Guard helicopter was flying around the area where the hikers might be , authorities said .

When the avalanche danger lowers , three teams will head to the probable areas , Meyers said .

`` It could be today , it could be tomorrow , '' he said .

Temperatures were in the 20s overnight , with winds higher up the mountain .

The mountain rises 11,239 feet above sea level , with a vast base that stretches over 92 miles -LRB- 148 kilometers -RRB- . It is the highest mountain in Oregon , a dormant volcano with steam constantly spewing from holes , according to the Web site mthood.info .

CNN 's Nick Valencia contributed to this report .

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Three began hike on Oregon 's Mount Hood on Friday morning

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They were reported missing 21 hours later ; one found dead Saturday

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Authorities searching for the two others

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Threat of avalanches hindering search , authorities say